Cellular networks have limited capacity for transmitting and receiving voice calls and electronic data (e.g., text messages, multimedia messages, email, web browsing, etc.) between base stations and cellular telephones due to the finite frequency bandwidth or spectrum available to the network. A voice call and/or electronic data can be delivered to a cellular telephone using a radio frequency (RF) signal at a certain operating frequency. Capacity in cellular networks may be increased by implementing a frequency reuse scheme. In such a scheme, RF signals with the same operating frequency may be used by different cellular telephone users in different cells. Typically, the different users are several cells apart to limit the interference between the RF signals of the different users. However, significant interference between the users may still exist which can decrease quality of the voice calls or corrupt the electronic data received by the different users.
An approach to reducing interference due to frequency reuse may include tilting antenna beams of base stations of cellular networks such that the transmitted RF signal is confined to the cell. Beam tilting may be performed in several different ways including mechanical, electrical, and optical methods. Electronic beam tilting can be used in cellular applications as well as satellite communication networks, smart weapons, radar applications, and other RF systems where RF signals may interfere with each other.
Decreases in a quality of service in such systems and applications can occur when two or more RF signals are in phase with each other resulting in the RF signals destructively interfering with each other. Beam tilting may be achieved by varying the phase of the transmitted RF signal. The phase variation can be performed in two ways, for example. First, the phase can be adjusted by changing the operating frequency of the signal. This may not be desirable in some applications, such as cellular applications, because the transmitted signal would not be properly decoded at the receiver. Secondly, electronic phase shifters can be used to vary the phase at a fixed operating frequency. However, traditional electronic phase shifters may be expensive as well as may have high power consumption requirements.